Alcelaphine herpesvirus 1 genes A7 and A8 regulate viral spread and are essential for malignant catarrhal fever.

Alcelaphine herpesvirus 1 (AlHV-1) is a gammaherpesvirus that is carried asymptomatically by wildebeest. Upon cross-species transmission to other ruminants, including domestic cattle, AlHV-1 induces malignant catarrhal fever (MCF), which is a fatal lymphoproliferative disease resulting from proliferation and uncontrolled activation of latently infected CD8+ T cells. Two laboratory strains of AlHV-1 are used commonly in research: C500, which is pathogenic, and WC11, which has been attenuated by long-term maintenance in cell culture. The published genome sequence of a WC11 seed stock from a German laboratory revealed the deletion of two major regions. The sequence of a WC11 seed stock used in our laboratory also bears these deletions and, in addition, the duplication of an internal sequence in the terminal region. The larger of the two deletions has resulted in the absence of gene A7 and a large portion of gene A8. These genes are positional orthologs of the Epstein-Barr virus genes encoding envelope glycoproteins gp42 and gp350, respectively, which are involved in viral propagation and switching of cell tropism. To investigate the degree to which the absence of A7 and A8 participates in WC11 attenuation, recombinant viruses lacking these individual functions were generated in C500. Using bovine nasal turbinate and embryonic lung cell lines, increased cell-free viral propagation and impaired syncytia formation were observed in the absence of A7, whereas cell-free viral spread was inhibited in the absence of A8. Therefore, A7 appears to be involved in cell-to-cell viral spread, and A8 in viral cell-free propagation. Finally, infection of rabbits with either mutant did not induce the signs of MCF or the expansion of infected CD8+ T cells. These results demonstrate that A7 and A8 are both essential for regulating viral spread and suggest that AlHV-1 requires both genes to efficiently spread in vivo and reach CD8+ T lymphocytes and induce MCF.

Antiviral activity of porcine interferon omega 7 against foot-and-mouth disease virus in vitro.

Foot-and-mouth disease (FMD) is a disease of worldwide economic importance, and vaccines play an important role in preventing FMDV outbreaks. However, new control strategies are still needed since FMDV outbreaks still occur in some disease-free countries. Currently, interferon (IFN)-based strategies have been demonstrated to be an efficient biotherapeutic option against FMDV; however, interferon omega (IFN-ω) has not yet been assessed in this capacity. Thus, this study evaluated the antiviral activity of porcine IFN omega 7 (PoIFN-ω7) against FMDV. After the PoIFN-ω7 was expressed and purified, cell proliferation assays and quantitative real-time reverse transciption-polymerase chain reaction were used to evaluate the effective anti-cytopathic concentration of PoIFN-ω7 and its effectiveness pre- and post-infection with FMDV in swine kidney cells (IBRS-2). Results showed the rHis-PoIFN-ω7 fusion protein was considerably expressed using Escherichia coli BL21 (DE3) strain, and the recombinant protein exhibited significant in vitro protection against FMDV, including two strains belonging to type O and A FMDV, respectively. In addition, PoIFN-ω7 upregulated the transcription of Mx1, ISG15, OAS1, and PKR genes. These findings indicated that IFN-ω has the potential for serving as a useful therapeutic agent to prevent FMDV or other viral outbreaks in pigs.

Inhibitory effects of homoharringtonine on foot and mouth disease virus in vitro.

Foot-and-mouth disease (FMD) is a highly contagious disease that affects cloven-hoof animals including cattle, swine, sheep, goats, and lots of wild species. Effectively control measures are urged needed. Here, we showed that homoharringtonine treatment exhibited a strong inhibitory effect against two different strains of FMDVs (O/MYA98/BY/2010 and A/GD/MM/2013) in swine kidney (IBRS-2) cells. Further experiments demonstrated that homoharringtonine did not affect virus attachment or entry. Using time-of-addition assays, we found that the antiviral activity of homoharringtonine occurred primarily during the early stage of infection. These results demonstrated that homoharringtonine might be an effective anti-FMDV drug. Further studies are required to explore the antiviral activity of homoharringtonine against FMDV replication in vivo.

Antiviral effect of amiloride on replication of foot and mouth disease virus in cell culture.

Recently, amiloride was shown to potently suppress Coxsackievirus B3 (CVB3) replication. In the current study, we investigated whether amiloride could also exhibit antiviral activity against foot-and-mouth disease virus (FMDV), which belongs to the same family (Picornaviridae) as CVB3. We found that amiloride exerted antiviral activity in a dose-dependent manner against two strains of FMDV in IBRS-2 cells, with slight cytotoxicity at 1000 µM. Besides, amiloride did not inhibit the attachment and entry of FMDV in IBRS-2 cells, but prevented early viral replication. These data implied that amiloride could be a promising candidate for further research as a potential antiviral drug against FMDV infection.

A novel type I interferon, interferon alphaomega, shows antiviral activity against foot-and-mouth disease virus in vitro.

Recently, a novel type I interferon alphaomega (IFN-αω), also known as IFN-µ, was identified. However, the biological activity of IFN-αω remain poorly understood. In this study, the porcine IFN-αω (PoIFN-αω) was expressed, purified, and its antiviral activities assessed by its ability to inhibit the cytopathic effect caused by FMDV on IBRS-2 cells. In addition, q-PCR was used to evaluate the expression of IFN-stimulated genes induced by PoIFN-αω. It was found that PoIFN-αω exerted effective antiviral activity against FMDV pre- and post-infection. Additionally, PoIFN-αω induced the transcription of IFN-stimulated genes, including Mx1, ISG15, OAS1, and PKR genes. Our study reported a new indication of PoIFN-αω as an effective anti-FMDV agent for the first time.

In Vitro and in Vivo Antiviral Activity of Mizoribine Against Foot-And-Mouth Disease Virus.

Foot-and-mouth disease (FMD) is a highly contagious viral disease of cloven-hoofed animals, which has significant economic consequences in affected countries. As the currently available vaccines against FMD provide no protection until 4-7 days post-vaccination, the only alternative method to control the spread of FMD virus (FMDV) during outbreaks is the application of antiviral agents. Hence, it is important to identify effective antiviral agents against FMDV infection. In this study, we found that mizoribine has potent antiviral activity against FMDV replication in IBRS-2 cells. A time-of-drug-addition assay demonstrated that mizoribine functions at the early stage of replication. Moreover, mizoribine also showed antiviral effect on FMDV in vivo. In summary, these results revealed that mizoribine could be a potential antiviral drug against FMDV.

Type I Interferons: Distinct Biological Activities and Current Applications for Viral Infection.

The interferons (IFNs) are a primary defense against pathogens because of the strong antiviral activities they induce. IFNs can be classified into three groups: type I, type II and type III, according to their genetic, structural, and functional characteristics and their receptors on the cell surface. The type I IFNs are the largest group and include IFN-α, IFN-ß, IFN-ε, IFN-ω, IFN-κ, IFN-δ, IFN-τ and IFN-ζ. The use of IFNs for the treatment of viral infectious diseases on their antiviral activity may become an important therapeutic option, for example, IFN-α is well known for the successful treatment of hepatitis B and C virus infections, and interest is increasing in the antiviral efficacy of other novel IFN classes and their potential applications. Therefore, in this review, we summarize the recent progress in the study of the biological activities of all the type I IFN classes and their potential applications in the treatment of infections with immunodeficiency virus, hepatitis viruses, and influenza viruses.

Antiviral activity of merimepodib against foot and mouth disease virus in vitro and in vivo.

Foot and mouth disease virus (FMDV), a member of family Picornaviridae, belongs to the genus Aphthovirus, which causes foot and mouth disease (FMD), a highly transmissible disease that affects cloven-hoof animals. In spite of the fact that efficient vaccines are available, effective antiviral molecules for FMD are needed to reduce viral infection during early stages of infection. In this study, merimepodib was found to efficiently inhibit FMDV replication in a dose-dependent manner. The 50% inhibitory concentration (IC50) of merimepodib antiviral activity against two distinct FMDV strains (O/MYA98/BY/2010 and A/GD/MM/CHA/2013) was estimated to be 7.859 and 2.876 µM, respectively, while the 50% cytotoxic concentration (CC50) of merimepodib was found to be 47.74 µM. Furthermore, treatment with 30 µg merimepodib efficiently prolonged the survival time of suckling mice infected with FMDV. Taken together, these results suggested that merimepodib has the potential to be a novel antiviral agent against FMDV.

Antiviral activity of brequinar against foot-and-mouth disease virus infection in vitro and in vivo.

Foot-and-mouth disease (FMD) is one of the most highly contagious animal disease that affects cloven-hoofed animals. However, the FMD vaccine does not provide effective protection until adaptive immune protection elicited by the vaccination occurs. Therefore, an alternative application of antiviral agents for inhibition of the FMD virus (FMDV) is needed. Here, we demonstrated that brequinar could exhibit antiviral activity in swine kidney cells (IBRS-2 cells) infected with two different FMDV serotypes. Subsequently, in vivo activity of brequinar was confirmed in a mouse model of infection. Specifically, brequinar at a concentration of 50 µg, provided 25% protection for 5 days following FMDV challenge. These results suggested that brequinar could be used as effective antiviral agent against FMD.

Antiviral activity of porcine interferon delta 8 against foot-and-mouth disease virus in vitro.

Foot-and-mouth disease (FMD) is one of the most devastating diseases affecting livestock. Since vaccines fail to provide protection until seven days post-vaccination, the application of anti-viral molecules is imperative for suppressing the spread of FMDV prior to development of an adaptive immune response. Interferons (IFNs) are effective for the host to fight FMDV infections; however, a novel type I IFNs, interferon delta (IFN-δ), has not been investigated for their antiviral effects against this virus. Thus, this study investigated FMDV infection, upon pre- and post-treatment with PoIFN-δ8. Real-time quantitative PCR was used to quantify the expression levels of IFN-stimulated genes (ISGs), including ISG15, OAS1, PKR, and Mx1. Results showed the PoIFN-δ8 lacking its signal sequence was efficiently expressed in Escherichia coli, and the purified recombinant PoIFN-δ8 exerted a significantly protective effect against two different serotypes of FMDV in IBRS-2 cells. In addition, PoIFN-δ8 induced the expression of IFN-stimulated genes. These findings highlight the significance of PoIFN-δ might serve as an antiviral agent for the prevention of FMDV in pigs and will stimulate the study of exploiting the potential biological functions of IFN-δ in the future.